Carbon black, in the form of small pellets, is a major component of many synthetic rubbers such as that used in automobile tires. A problem encountered in the carbon black industry is that the pellets may be contaminated by metallic particles. One suggested method of removing that metallic material from a carbon black pellet stream is the known belt magnetic separator. The pellets are dumped onto a moving conveyor belt having a magnetic head pulley. As the conveyor reverses direction about the head pulley, the nonmagnetic carbon black pellets fall off ahead of the conveyor. However, magnetic material is held to the conveyor as it continues around the head pulley, and that material can be collected separately from the carbon black.
The magnetic pull on contaminants in the pellet stream is greatest immediately adjacent the conveyor. Thus, magnetic contaminants resting directly on the conveyor belt are easily separated. However, material set away from the conveyor belt by a pile of carbon black pellets may break free from the magnetic pull of the pulley and fall with the carbon black.
An object of the present invention is to provide a means for spreading the contaminated carbon black evenly across the conveyor belt as a thin sheet. All particles are thereby subjected to a strong magnetic pull as the conveyor belt is driven around the magnetic head pulley. Preferably, the sheet of particulate material is only about one pellet thick because the magnetic pull decreases with distance from the belt and because small magnetic particles resting on one or more carbon black pellets might be carried by those pellets in their fall away from the magnetic pulley.